Check out example codes for "use where instead of join". It will help you in understanding the concepts better.

Code Example 1

# using WHERE ANSI-89 syntax
SELECT *
  FROM TABLE_A a,
       TABLE_B b
 WHERE a.id = b.id

# using JOIN ANSI-92 syntax
 SELECT *
  FROM TABLE_A a
  JOIN TABLE_B b ON b.id = a.id

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